1. Field of the Invention
The present invention relates to a building board, and method and apparatus for coating a building board. In particular, it relates to a building board having concavities such as grooves to which a shade-coating is effectively applied to obtain an aesthetically enhanced building board.
2. Description of the Prior Art
Building boards having grooves in its surface are widely used, and the surface is generally coated to obtain an aesthetically enhanced building board. In a conventional coating method, a spray coating of a joint portion color is applied to a surface of a substrate such as a cement board in such a manner that grooves are also coated, and then a coating of an appropriate color is applied to the surface by a roll coater method, a curtain flow coater method or the like.
FIG. 37 is a cross-section of a conventional building board having its surface subjected to surface coating by a roll coater method. The building board (a) has grooves 5 in its surface. In the surface coating, a coating (a1) of a joint portion color is first formed over the whole surface including the grooves 5 by a spray coating method, and then an appropriate coating (a2) is formed on convexities (surface plateau) by a roll coater method. In a roll coater method, if the convexities are even as shown in FIG. 37, a uniform coating is formed. However, with respect to a building board having a surface with considerable irregularities, a non-uniform coating is formed. Accordingly, appropriate surface coating cannot be effected. Further, it is impossible by a roll coater method to apply a specific coating to the grooves 5. The grooves 5 are coated merely with the spray coating (a1) of a joint color, and thus all surfaces defining the grooves 5 have substantially the same color depth. It is, therefore, impossible to impart a delicate impression of shading to the grooves 5. If a sponge roll is used, a uniform coating can be applied to a surface with irregularities to some extent. Practically, however, this is only possible up to an up-and-down roughness of about 3 mm. Further, a desired specific coating cannot be applied to the grooves 5.
In a curtain flow coater method or the like, a coating to some extent can be applied even to an up-and-down surface with considerable roughness of a building board, and the coating can be applied also to the grooves continuously. However, the coating has uniform thickness and color depth. Accordingly, a coating with shading cannot be applied to the grooves. Further, although a somewhat suitable coating can be applied to rectilinear grooves, a uniform coating cannot be applied to curved grooves or grooves with a varying groove width. Moreover, coating by a curtain flow coater method has a lower limit in a width of a groove to which it can be applied. Accordingly, if grooves are narrow they are difficult to coat in a satisfactory manner.
Due to the above problems, conventional surface-coated building boards unavoidably give a person viewing the boards a strong impression of flatness as a whole. In particular, such boards have a poor impression of shading at concavities such as grooves. It is impossible using such building boards to obtain a highly aesthetic building board. Furthermore, both of the above-described methods are directed to application of a coating to a building board having a relatively flat surface geometry, for example, a building board having a flat surface formed with several linear grooves. Accordingly, such methods related to coating flay surfaces are incapable of applying a desired coating to a building board having a surface with complicated irregularities or a complicated pattern. In recent years, it has been possible to easily prepare a building board having a complicated surface geometry by an extrusion molding method or a cast molding method which is highly formative. These extruded building boards have increased the demand to apply a desired coating to a surface having complicated irregularities, in particular, concavities in the surface. However, an aesthetically satisfactory surface coating has not yet been obtained.
It is an object of the present invention to provide a building board having a highly aesthetic surface which has not been obtained by any conventional coating methods. In particular, this object is achieved through application of a coating capable of giving a viewer strong impression of shading to a complicated linear or curved concavity having a varying cross-sectional geometry in a crosswise direction of the concavity. Using the method of the present invention, one can obtain a building board having a highly aesthetic surface.
It is another object of the present invention to provide coating method and apparatus which are capable of easily applying a coating exhibiting an enhanced impression of shading to concavities with complicated geometries formed in a surface of a building board.
According to the present invention there is provided a building board having its surface provided with a concavity having a bottom and right and left sides, the concavity being coated in such a manner that a color of the coating is deepest in the bottom and gradually becomes lighter in the sides from the bottom to the surface.
According to the present invention there is provided a building board having its surface provided with a concavity having a bottom and right and left sides, and the right and left sides of the concavity are coated in such a manner that an average color depth of the coating in the side having a larger horizontal component is lighter than that in the side having a smaller horizontal component when the concavity is horizontally projected from above.
In the building board constructed as described above, the coating in the concavity has an emphasized shade difference, thereby giving a viewer strong impression of shading. As a consequence, color depth is emphasized thereby obtaining a highly aesthetic building board.
In the present invention, there is no particular restriction with respect to the cross-sectional geometry in crosswise direction of the concavity. The cross-sectional geometry in crosswise direction of the concavity is not restricted to one having clear demarcation points between a bottom and a side and between a side and a surface, for example, a substantially gutter-like cross-section. It may be one having unclear demarcations or continuous one (i.e., unangular one). It includes any one having an apparent xe2x80x9cbottomxe2x80x9d and apparent xe2x80x9csidesxe2x80x9d. Accordingly, the term xe2x80x9cbottomxe2x80x9d used herein has such a wide meaning that a xe2x80x9cbottomxe2x80x9d includes a portion recognizable as an apparent xe2x80x9cbottomxe2x80x9d, and the term xe2x80x9csidexe2x80x9d used herein has such a wide meaning that a xe2x80x9csidexe2x80x9d includes a portion recognizable as an apparent xe2x80x9csidexe2x80x9d. Each of the xe2x80x9cbottomxe2x80x9d and xe2x80x9csidexe2x80x9d may not be a flat surface, and may be an irregular surface, a curved surface or the like.
The present invention discloses a method for coating a building board having; a bottom and right and left sides, the method comprising:
jetting paint as a regulated jet in the form of a paint membrane while jetting air along right and left edges of the paint membrane by means of a coating nozzle provided with a center orifice for jetting paint and air-jet orifices for jetting air along right and left edges of the paint membrane to carry out the coating of the concavity in such a manner that paint atomized into minute particles by the jetted air is mainly applied to the sides of the concavity. According to this method, color of right and left portions of the resulting coating pattern is light as compared with that of a center portion and becomes gradually lighter with distance from the center portion. By virtue of this, it is possible to easily apply a coating to a concavity in such a manner that a color of the coating is deepest in the bottom and gradually becomes lighter in the sides from the bottom to the surface.
The present invention further discloses a method for coating a concavity in a building board having its surface provided with a concavity having a bottom and right and left sides, the method comprising:
taking an image of the concavity in the surface by image pick-up means such as a digital camera to obtain information on a cross-sectional geometry in a crosswise direction of the concavity from the picked-up image data, and
controlling a level and an inclination angle of a coating nozzle based on the information, thereby permitting the color depth of one side to be lighter or deeper than that of the other side.
Using this method, the level and inclination angle of the coating nozzle to be continuously controlled by using the data gained from image processing, so it is possible to easily apply a coating to concavities having any plan geometry such as straight curved or zigzag one.
It is preferred that the information on a cross-sectional geometry in the crosswise direction of the concavity be coordinates of both ends of the bottom of a cross-section of the concavity and coordinates of intersection points of the right and left sides with the surface of the building. Lengths of line segments into which a line segment connecting the intersection points of the right and left sides and the surface of the building board are divided by intersection thereof with a vertical line passing through the middle point of the bottom and calculated based on the coordinate information. A level and an inclination angle of the coating nozzle can be so controlled that an average color depth of the side under the larger line segment is lighter than that of the side under the smaller line segment.
Further, the present invention discloses an apparatus for coating a concavity of a building board having its surface formed with a concavity having a bottom and right and left sides, the coating apparatus comprising:
a conveyor for transferring a building board, and at least one coating nozzle for applying a coating to a concavity in a surface of a building board transferred by the conveyor, each of the coating nozzles being adjustable in its level and jetting direction, the level and jetting direction of the coating nozzle being controlled based on information on a cross-sectional geometry in crosswise direction of a concavity to be coated.
By using the coating apparatus, it is possible to easily prepare a building board aesthetically enhanced in such a manner that a color of the coating is deepest in the bottom and gradually becomes lighter in the sides from the bottom to the surface or a highly aesthetic building board having color depth difference between the right and left sides.
Preferably, the coating apparatus further comprises means for taking an image of the concavity, and means for controlling a level and an inclination angle of a coating nozzle based on information obtained by taken image data, thereby effecting control of the level and inclination angle of the coating nozzle in line with the geometry of the concavity. More preferably, the coating apparatus further comprises means for detecting edges as intersections between the sides and the surface of the concavity. Based on the information on the edges, control of the position of the coating nozzle and suspension/resumption of the paint jetting from the coating nozzle, change of pressure of paint jetting from the coating nozzle, etc. are effected, thereby enabling application of an aesthetically enhanced coating to the concavity.
The coating apparatus may be used alone. Further, more than one coating apparatus may be placed at angles with each other to cause a building board to be coated to successively pass through the plurality of coating apparatus, thereby continuously applying a coating aesthetically enhanced as described above to a number of concavities